Cotton filled calender roll and method of making



y 21, 1968 v. L. WILKINSON 3,383,749

COTTON FILLED CALENDER ROLL AND METHOD OF MAKING Filed June 28, 1966 INVENTOR. VERNON L. WILKINSON ATTORNEY.

United States Patent 3,383,749 COTTON FILLED CALENDER ROLL AND METHOD OF MAKING Vernon L. Wilkinson, Westfield, Mass., assignor to B. F. Perkins & Son, Inc., Holyoke, Mass., a corporation Filed June 28, 1966, Ser. No. 561,217 2 Claims. (Cl. 29125) This invention relates to improvements in calender rolls adapted for operating on paper, fabric and the like.

Its principal objects are directed to the provision of a novel calender roll, characterized by a heat resistant body, and adapted for use in a calender or calender stack in cooperation with another roll or rolls which are similar or have different characteristics and between which rolls a web of paper or fabric may pass.

Various novel features and advantages of the invention will be hereinafter more fully referred to in connection with the accompanying description of the invention in its present preferred form. In the drawing, the figure is a side elevational view of the roll embodying the novel features of the invention.

The roll of the invention has a central shaft 2 and end members 6 suitably secured thereon, between which members, there is provided a body 4 formed from sections or discs 8 which are held in pressed-together relation by the end members, the end members being held or locked on central shaft 2 by any suitable means.

The discs or sections 8 are formed from fibrous material, preferably from non-woven structures manufactured either on conventional textile web forming equipment or wet lay processes as used in the paper industry. The discs are preferably formed of some more or less yieldable material and cotton threads have been found to be suitably adapted for the purpose of the invention.

These sections have openings therethrough for the shaft. To prevent the discs or sections from turning on the shaft, there may be keys or the like receivable in splines in the discs.

The discs or sections are arranged in stacked relation on the shaft and pressed together and confined in their pressed-together relation by the end members.

The peripheral surface of the roll is then worked down to the desired diameter and surface by grinding, turning, or some other suitable operation.

The roll of the invention may be employed in some instances adjacent to a metal roll or it may be employed in cooperation with a similar roll, or a laminated roll of some other form, all depending upon the use to which the roll is to be employed.

The cotton filling employed is a specially treated long staple cotton upgraded so as to adapt same to withstand the high temperatures and high pressures encountered in many calendering operations of the present day. The cotton fiber is changed in the respect that it is thermally upgraded by the removal therefrom of the impurities (residual oils, fats and waxes) so as to allow a pure cellulose for the filling in what constitutes a heat resistant roll. So conditioned, the fiber is stronger in tension and more absorbent.

The cotton plant, a member of the mallow family, Malvecea, has received intensive studies from both morphologists and physiologists.

After pollination, the cotton boll ripens. Instead the boll, the ovules mature simultaneously with the vital covering seed hairs.

During the early growth stages, after pollination, the hair grows only in .a longitudinal direction, becoming tubelike and elongated and being surrounded by a wall of cellulose. The outside of the latter membrane consists of wax and fatty substances, which are impermeable to gas and water and provide the fiber with its silkiness and "ice luster. After a few days, another layer of cellulose is deposited on the inside of the cell wall. Concentric rings are formed, corresponding to the days of growth. The hair lives until the time of boll opening. As it dries, its tubelike form collapses and becomes twisted in its length, exceeding the diameter from 1000 to 3000 times. The characteristic twists correlate with spiral fibril structures in the secondary wall. There are reversals of this twist during the convolutory growing process.

Unlike other fibers obtained from plants, the cotton fiber is a single elongated cell resembling a collapsed, spirally twisted tube with a rough surface. The thin cell wall of the fiber has 200-400 natural twists, or convolutions, per inch. The fiber is fiat, twisted, and ribbon-like, with a wide inner canal (lumen). Chemically, the fiber is about cellulose and 6% moisture; the remainder being impurities. The outer surface of the fiber is covered with a protective waxlike coating to define a somewhat adhesive quality. It is this waxlike coating, together with the impurities, which the invention seeks to eliminate.

When the 'bolls open, the fiber and seed, or seed cotton, is harvested by hand or machines. The fully matured staple is fiber separated from the seed by gins. This cotton fiber is compressed into bales, covered with jute bagging, and bound for ease of handling and passed through commercial channels, eventually reaching cotton mills, there to be broken open and the cotton is blended, cleaned, carded, and spun into yarns.

Yarn quality depends upon the origin, average staplelength distribution, color, and feel. To ensure a desired uniformity the product quality, batches of raw fiber, different in staple length and other characteristics, are processed by blending together. One important consideration is the detection of large proportions of immature and dead fibers, because this variance will affect the spinning operation. Too, cotton can be overginned so as to result in fiber damage through severe mechanical handling and desiccation by the air driers. Gin drying is carried out prior to removal of cotton fibers from the seed by gin saws. With the advent of machine-picked cotton, the ginner has had to contend with more trash because the machines pick parts of stalk and leaves and other components of the plant as well as the bolls. To overcome this, longer drying programs and more elaborate equipment are now being used to clean the cotton. This tends to shorten the fibers and make them more brittle and compressionally stiffer.

Although the ginner removes much of the trash through hot-air drying, trash often still remains to be removed later from the baled cotton by the processor using opening machines. The cotton fibers must then be parallelized by carding to form them into fine webs which are drawn into slivers. Slivers are again mixed with other slivers. Drawing the slivers with a slight twist on drawing frames containing multirollers produces then a greater degree of parallel orientation. High-speed drawing yields higher production rates, but less-uniform yarn. The sliver is then twisted into roving to give a more compact and stronger product. This product is wound into bobbins and then spun into yarn.

While the original harvested cotton is relatively free of oil, oils are encountered in the spinning and other manufacturing processes, same normally being exploited for purposes of providing lubricity during drawing and/or spinning, as well as a reducing static electricity during processing. It is the presence of these residual oils that is of primary concern in this invention.

The backbone of the chemical structure of cotton is cellulose, which may be regarded as a series of building blocks of glucose units (pyranose rings forming long chains), each with two primary and two secondary OH 3 groups. The latter control the chemical reactivity of the whole structure.

The structural formula of cellulose, which is:

shows how the individual anhydroglucose (pyranose) units forming the repeating units are linked at the one and four position through the B-glucoside bonds. The disposition of these chains in relation to each other determines the macroscopic properties of the fibers, that is, whether they are crystalline or unordered (amorphous). These two types of structural characteristic of cotton infiuence both its chemical and physical properties. The crystalline portions give the fiber strength, whereas the amorphous areas influence most of its rheological properties. Long-range elasticity is dependent upon amorphous structure which plays an active role in crease resistance. Cottons cellulose is mostly crystalline, and the cohesion of the molecules is the result of Van de Waals forces and fairly strong hydrogen bonding repeated many times between the glucose units without any primary chemical bonds, so that when the fiber reacts to a large strain consistent with fabric creasing, there are no direct chemical bonds to promote the strained fiber to its original configuration. Its reaction to such subugation relies upon the entangled network of the amorphous molecular system. This accounts for cottons poor elastic recovery. However, this deficiency is counter-balanced when the fiber is wet. The amorphous areas swollen with water molecules can act as an internal lubricant and release local strains in the long chain held in the more strongly bound crystalline regions, making for a more uniform stress pattern. Creases are thereby released, and the fiber is also allowed to carry heavier loads as a result of chain bonding by the water molecules.

The amorphous areas are chemically more accessible than the crystalline to reactivity. All the swelling takes place in the former areas, which are hydrophilic. Complete solubilization by water is prevented, however, by the strong hydrogen-bonding effects between the long chains. Short-chained cellulose such as is found in paper can be solubilized in water. The OH groups are capable of chemical addition such as esterification. With acetic acid, acetate rayon is formed, and with nitric acid, guncotton. Blocking of the OH groups reduces cottons hydrophilic properties with complete chain retention, however. These reactive OH groups permit the use of chemical additives, for example, for fiame resistance, crease resistance, and many other properties to increase the fibers usefulness.

The approach to the development of a heat-resistant calender roll has been along the avenue of the treatment of the cotton to thermally upgrade same via a wet finishing process.

Recognizing that the impurities in cotton constitute 611% of the cotton and are made up of residual oils, nitrogenous matter (protoplastic residues), mineral matter (calcium and magnesium salts), pectic material (mainly calcium and magnesium pectates), waxes (a complex mixture of wax alcohols, free fatty acids, and esters of wax acids), and an unclassified mixture of pigments and resins, it has occurred that the removal of such impurities might have its effects in improving the roll.

I have determined that cotton so treated is considerably more resistant to deterioration by heat than cotton not so treated.

Some of such impurities can be removed with inorganic solvents, some by water steeping, some by acid steeping, some by alkali boiling.

Warp sizing and some impurities can be removed in soap and surface-active agents.

Most of the waxes must be removed by emulsification in hot alkaline solutions, they being the most difiicult to remove. Likewise as to the fats, proteins and pectins.

The materials being so boiled for the purposes of the invention are combinations of loose cotton and yarn.

Bales of cotton are used made up of fine threads with a minimum of loose fiber, same being obtained from mills as waste, cut by a suitable cutting machine into shorter threads of various lengths between a minimum of l and a maximum of 3" and processed through pickers so as to open and loosen same.

The material is then run into the kier in a moist condition and is evenly packed or plaited down.

The prepared caustic kier liquor is run in at temperatures approximating 120 to 160 F. The hotter it is, the easier it is to bring the mixture to a boil.

A pump and heater circulation system consists of the kier proper, centrifugal pump, heat exchanger and temperature controls, by which system live steam is admitted to the kier for the circulation of the caustic liquors.

The length of the boil is from 23 hours to as much as 8-10 hours, depending upon the strength of the alkali solution, the type of goods and the results desired.

The kier boiling liquors are in general solutions of one or more alkalies including caustic soda, sodium carbonate, sodium silicate and pine oil soap and other wetting-out agents.

The liquor softens the waxes and pectins and other noncellulosic components of the raw cotton.

The boiling process removes the oils, grease, dirt and other foreign matter of the raw cotton so as to leave practically pure cellulose.

When the boil is complete, the pressure is released and a hot water flush, introduced to the top of the goods, is allowed to filter down therethrough so as to wash out the caustic and the dissolved substances, same being normally followed with a cold water flush.

The normal chlorine bleaching operation is dispensed with inasmuch as bleaching serves to weaken the fiber which is not desired.

The described processing elfects desirable chemical and physical changes as follows: the cellulose is regenerated and the fiber has grown larger in diameter so as to make it stronger and tougher while yet losing none of its elongation properties, in fact while increasing the resiliency thereof. Being tubular in shape, the characteristic of increased water absorbency is attained.

Elongation is a chief desideratum in the respect that no more elongation following treatment is desired than preceding treatment. It is known that the less elongation in esse, the more brittle the fiber, and the more elongation, the more flexible the fiber.

Resiliency is another chief consideration, it being the belief that if one were to make cotton more resilient, energy put into the fiber during compression of the face of the roll will be used up as the resilient fiber returns to its normal position. If the fiber were not resilient, the energy put into it during compression would be converted into heat.

Most significantly of all, the fiber is heat resistant, being constituent of pure cellulose with the low temperature contaminates being eliminated therefrom.

To dramatize the results of the aforedescribed processing, specimens of fiber were taken at random and sampled for tensile properties. The samples were conditioned at 70 F. and 65% relative humidity and tested in accordance with A.S.T.M. Designation D 540-59 on an Instron Universal Testing Machine. The specimens were tested on a 0.25 inch gage length with a crosshead speed of 0.1 inch per minute, a chart speed of 10 inches per minute, and on a 10 gram range. Autographic integrator readings were recorded, from which the energy to break toughness was calculated.

The water absorption of each sample was determined by immersing a specimen weighing approximately /2 gram in distilled water for two minutes. The specimen was then placed between two blotter sheets and run through a laboratory wringer with rubber covered rollers under a pressure of 60 pounds before re-weighing.

The cotton is bleached and becomes considerably more absorbent. Absorbency being essential in working out marks, the more absorbent the fiber, the better it will absorb the mark removing liquid.

Users of the rolls hereof have been averaging 50% more life than in the case of rolls filled with regular cotton.

Specimen 1, the heat resistant cotton of the invention, disclosed as follows:

Specimen 2, a regular cotton filling, disclosed as follows:

Breaking Elonga- Energy, load, tion, inchgrams percent grams Average of 50 values 1. 24 10. 2 0. 006 Maximum... 2. 00 27. 0 0. (112 Minimum... 0. 52 3. 6 0. 002

Sample standard deviation.-. 0. 41 4. 4 0. 0028 WATER ABSORPTION Sample Percent 71.1

Average 71.3

Average 56.0

Such tabulation discloses that the breaking strength of the cotton processed according to the invention is better than doubled over the conventional cotton.

Both elongate on stretching about the same.

The cross section of the fiber is altered in the respect that it is larger in diameter, by as much as /3 to /z, following treatment.

The swelling is a mild form of mercerization.

Same aids in removing the oils.

The so-treated material is capable of resisting charring according to a certain scale.

When a cotton filled roll is brought into operating relation with a steel roll in a calender, there is a physical distortion of the filled roll (or any soft roll) by the build-up at the entering side of the nip, of material at and immediately adjacent to the surface of the filled roll. The higher the initial modulus (resistance to stretch), the lesser amount of build-up or puddle at the nip. The less of this build-up, the less working of the surface masses as they are worked through the nip. Less nip action as described generates less friction and less heat.

It is during this very same nip action that fibers are placed under extreme tensile stresses, and that high tensile strength of the modified cotton fibers is of paramount importance.

Thus we have a high initial modulus so as to minimize heat generated through roll, surface distortion, and high tensile strength for the provision of a stable body of filling under extreme stresses.

Oils have a low burning coefiicient and as long as they are present, they will burn prior to the cellulose in the cotton. Hence the desideratum of removing the residual oil's so as to allow working with pure cellulose so as to define a thermally upgraded fiber which is less subject to burning and heat deterioration.

The so-processed cotton not only resists heat but offers improved resiliency in a filled roll.

I claim:

1. A calender roll of the class described comprising in combination, a rigid central shaft, disc-like members disposed in adjacency on said shaft, said disc like members being formed of cotton fibers and threads pretreated with a removal therefrom of all residual oils and fats and waxes to allow a pure cellulose filling for enhancing the heat resistant quality.

2. In a method of making a cotton filled calender roll, the steps of removing all impurities from the cotton fibers and threads preliminary to assembling the roll, forming the cotton fibers and threads into disc-like members with openings therethrough, arranging the disclike members in stacked relation on a shaft, and pressing and confining the disc-like members in pressed-together relation to form a calender roll.

References Cited UNITED STATES PATENTS 775,438 11/1904 Beck 29125 861,888 7/1907 Perkins 29125 X 1,785,265 12/1930 Lade 29-125 X 1,973,690 9/1934 Lade 29-125 3,291,039 12/1966 Christie 29125 X OTHER REFERENCES Matthews: Textile Fibers 5th ed. pp. 293-294; Wiley, New York.

LOUIS O. MAASSEL, Primary Examiner. 

1. A CALENDER ROLL OF THE CLASS DESCRIBED COMPRISING IN COMBINATION, A RIGID CENTRAL SHAFT, DISC-LIKE MEMBERS DISPOSED IN ADJACENCY ON SAID SHAFT, SAID DISC LIKE MEMBERS BEING FORMED OF COTTON FIBERS AND THREADS PRETREATED WITH A REMOVAL THEREFROM OF ALL RESIDUAL OILS AND FATS AND WAXES TO ALLOW A PURE CELLULOSE FILLING OR ENCHANCING THE HEAT RESISTANT QUALITY. 